The present invention relates to a process and apparatus for the production of a flowable reaction mixture from at least two flowable reactive components. The components react with one another to form solid material or foam material. The reactive components are injected into a mixing chamber and are mixed in a continuous flow. The mixture stream issuing from the mixing zone is throttled, as known from European patent 70,486.
A mix head for a similar process is disclosed in German Pat. No. 2,327,269 and U.S. Pat. No. 3,975,128. In the process described in these references, an outlet channel is arranged at right angles directly downstream of the mixing chamber. The outlet channel stabilizes the reaction mixture and can be cleaned by the associated discharging piston. It has been attempted to use the discharging piston to throttle the reaction mixture stream issuing from the mixing chamber. In the case of reactive components which are difficult to mix, throttling makes it difficult to stabilize the mixture stream to an adequate extent before it enters the mold cavity. Thus, the reaction mixture splashes out of the exit opening of the outlet channel and does not form a closed flow front.
Another known mix head (see, German patent 2,612,812 and U.S. Pat. No. 4,141,470) uses a transverse slide which is disposed, as throttling component, between the mixing chamber and the outlet pipe and which is provided with a through-flow opening. The desired through-flow cross-section can be adjusted by displacing this throttling component. In order to clean the mixing chamber and outlet pipe, the throttle slide is brought into the cleaning position so that the discharging piston can pass through the through-flow opening. This mix head has a relatively long structural length. With this mix head, it is difficult to precisely control the throttling component and the discharging piston to prevent these two elements from colliding. The resultant long structural length of the discharging piston is also unfavorable since it is possible that a film of reaction mixture may remain between the discharging piston and the walls of the mixing chamber and the outlet pipe may cause the discharging piston to adhere to the walls leading to the blockage of the piston. To prevent this from occurring, an over-sized drive means must be provided for the discharging piston. Because of the risk that the discharging piston may buckle, it must possess a specific minimum diameter relative to its length. Therefore the cross-sectional dimensions of the mixing chamber and the outlet pipe cannot be as small as desired. A further disadvantage is that the cross-sections of the mixing chamber and the outlet pipe must be identical.
Although the device according to European patent 70,486, does not possess the disadvantages of the aforementioned mix heads, it does require a large structural outlay and consequently is of an unwieldy size. In this device, the mixture stream is throttled on exit from the mixing chamber and then passes tangentially into a cyclone stream.
The goal of the present invention was to provide a process and an apparatus wherein even when processing reactive components which are difficult to mix, the rapid stabilization of the mixture stream following throttling is further improved. The new apparatus must require a lower structural outlay and possesses small dimensions. Finally, the apparatus must not be susceptible to breakdown, must be operationally reliable and must be self-cleaning.